A note on the concepts of age distribution and transit time in natural reservoirs

Abstract

A brief review is given of the concepts age distribution, transit time distribution, turn-over time, average age and average transit time (residence time) and their relations. The characteristics of natural reservoirs are discussed in terms of these concepts, and a classification is proposed based on whether the average age is larger, equal to or smaller than the average transit time. Some examples illustrate the differences between these various cases.